Method for thinning fruit

ABSTRACT

The present invention relates to a method for thinning fruit by using the active substance metamitron and corresponding metamitron-containing fruit thinning formulations.

The present invention relates to a method for thinning fruit usingmetamitron-containing thinning formulations.

Economically speaking, thinning is widely considered to be the mostimportant measure in pome fruit growing and in the commercialcultivation of a large number of other fruit crops. Thinning isunderstood as meaning the reduction in number of the pollinated flowersor of the number of fruit by mechanical means (by machine or hand) or bychemical agents. Advantages achieved through thinning are an improvedfruit size, color and/or quality together with a substantially improvedprofitability, the improvement of flowering in the year followingprolific flowering, or breaking and preventing biennial bearing inendangered varieties and young plantations, and avoiding the breaking ofoverloaded branches, pronounced exhaustion of the tree and theconcomitant reduced low-temperature resistance of the tree.

Thinning by hand is not an option in most growing regions owing to thecosts involved. Thinning with machines is possible to a limited extentonly, owing to, inter alia, the difficulty of combining efficacy withavoiding damage to the tree, as far as this is possible, owing to thesensitivity of varieties/trees and owing to the necessity of trainingthe trees into particular shapes (cultivation method).

This is why chemical thinning is of great importance. However, chemicalthinning agents which are currently used, such as urea and ammoniumthiosulfate (which are not licensed in Germany for this purpose) are notvery satisfactory with regard to their reliability and are frequentlypoorly tolerated by the plants at the concentrations used, which need tobe high. Other thinning agents which have not been licensed in Germanyto date or which are no longer licensed in Germany, too, are notentirely suitable for practice conditions with regard to their efficacyand plant tolerance since a very pronounced, variety-dependent lack ofreliability, which is influenced by the developmental stage of the fruit(flower) and the climatic conditions during and after the application,has always been observed. All of these known thinning agents act via thehormone balance of the plant (for example action via the plant hormonesauxin and ethylene in apples). The result is that undesired effects arefrequently observed with the formulations, such as, for example, areduced action at low concentrations, an unduly high degree of thinningunder adverse conditions at the time of application or in some casesindeed promotion of cropping. In addition, the agents from the carbamategroup, which are employed in many countries, only have a limited use asinsecticide.

The use of photosynthesis-inhibiting active substances for fruitthinning has been described in J. Amer. Soc. Hort. Sci. 115(1): 14-19(1990). The photosynthesis-inhibiting active substances stated thereinhave, however, not been used commercially as thinning agents since theirplant tolerance is unsatisfactory (for example in the case ofmetribuzin). W. Guzewski has studied the use of thephotosynthesis-inhibiting active substance metamitron (published inWarsaw Agricultural University- SGGW, Faculty of Horticulture, AnnualReport 1995, Warsaw 1996). According to this paper, spraying a “GoldenDelicious” apple variety with metamitron 7 days post-flowering at anapplication rate of 500 mg/l and 700 mg/l resulted in an increased fruitweight of 150 and 180 g, respectively, in comparison with a standard (98g). However, this method has not gained commercial importance as yet.The reason appears to be that plant damage (foliar necroses) can beobserved at the application rates described, and, when the circumstancesare unfavorable, an unduly high degree of thinning, which entails yieldlosses, occurs. Moreover, owing to the early application window (7 dayspost-flowering), the method is a floral thinning method.

Several years after Guzewski's publication, it has now been found,surprisingly, that efficient fruit thinning (as opposed to floralthinning) which avoids plant damage can be effected when a ready-to-usethinning formulation (for example a spray mixture) comprising 50-400mg/l metamitron is applied to the plant organs, in particular thefruits. In contrast to application rates of 700 mg/l, no unduly highdegree of thinning, which entails yield losses, and no foliar necrosesare observed. No, or barely discernable, damage to the crop plants isobserved. The formulations are therefore well tolerated by plants. Inaddition, the method according to the invention avoids biennial bearingin the plantations.

A late fruiting stage is understood as meaning, in this context, inparticular application at a later fruiting stage, preferably the 8 to 30mm, especially preferably the 8 to 17 mm, especially preferably the 10to 12 mm, fruiting stage or later. This procedure permits the selectivethinning of fruit after observing the actual cropping level up to aslate as including June drop. Such a method for efficiently thinningfruit at a late stage without damaging the plants has not been known todate.

The method according to the invention employs read-to-use fruit thinningformulations comprising 150-400 mg/l metamitron, which are novel andlikewise subject-matter of the present application.

The ready-to-use thinning formulations according to the inventionpreferably comprise 150-375 mg/l, very especially preferably 200-350mg/l, metamitron, a metamitron content of 350 mg/l being considered asideal for most purposes.

The fruit thinning formulations according to the invention areadvantageously prepared as water-based formulations.

In addition to metamitron, the fruit thinning formulations according tothe invention also comprise, if appropriate, additives, other thinningagents, growth regulators, foliar fertilizers and agrochemical activesubstances.

Suitable additives which may be present in the thinning formulationsaccording to the invention are further agrochemical active substancesand also crystallization inhibitors, wetters, emulsifiers or else water.

Suitable crystallization inhibitors which may be present in the thinningformulations according to the invention are all substances which canconventionally be employed for such purposes in agrochemicalcompositions. The following may be mentioned by way of preference:N-alkylpyrrolidones such as N-octylpyrrolidone and N-dodecylpyrrolidone,furthermore copolymers of polyvinylpyrrolidone and polyvinyl alcoholsuch as, for example, the polyvinylpyrrolidone/polyvinyl alcoholcopolymer which is known under the name Luviskol VA 64® (BASF),furthermore dimethylamides of alkylcarboxylic acids such asdimethyldecanamide, or the C₆₋₁₂-alkanecarboxylic acid dimethylamidemixture which is known under the name Hallcomid® (Hall Comp.), andfurthermore copolymers of ethylenediamine with ethylene oxide andpropylene oxide, such as, for example, the product known under the nameSynperonic® T 304 (Uniqema).

Suitable wetters are all the substances which can be employed for suchpurposes in thinning formulations. The following may be mentioned bypreference: alkylphenol ethoxylates, dialkylsulfosuccinates, such assodium dioctylsulfosuccinate, lauryl ether sulfate and polyoxyethylenesorbitan fatty acid esters. The use of silicone surfactants as wettersmay be mentioned in particular.

Suitable emulsifiers are all the customary nonionic, anionic, cationicand zwitter-ionic substances with surface-active properties which areconventionally employed in agrochemical compositions. These substancesinclude reaction products of fatty acids, fatty acid esters, fattyalcohols, fatty amines, alkylphenols or alkylarylphenols with ethyleneoxide and/or propylene oxide, and their sulfuric esters, phosphoric acidmonoesters and phosphoric acid diesters, furthermore reaction productsof ethylene oxide and propylene oxide, moreover alkylsulfonates, alkylsulfates, aryl sulfates, tetraalkylammonium halides,trialkylarylammonium halides and alkylaminesulfonates. The emulsifierscan be employed individually or else as a mixture. Emulsifiers which maybe mentioned by preference are reaction products of castor oil withethylene oxide in a molar ratio of 1:20 to 1:60, reaction products ofC₆-C₂₀-alcohols with ethylene oxide in a molar ratio of 1:5 to 1:50,reaction products of fatty amines with ethylene oxide in a molar ratioof 1:2 to 1:20, reaction products of 1 mol of phenol with 2 to 3 mol ofstyrene and 10 to 50 mol of ethylene oxide, reaction products ofC₈-C₁₂-alkylphenols with ethylene oxide in a molar ratio of 1:5 to 1:30,alkylglycosides, salts of C₈-C₁₆-alkylbenzenesulfonic acids, such as,for example, calcium salts, monoethanolammonium salts, diethanolammoniumsalts and triethanolammonium salts.

Examples of nonionic emulsifiers which may be mentioned are the productsknown under the names Pluronic® PE 10 100 (BASF) and Atlox® 4913(Uniqema). Others which are suitable are tristyrylphenol ethoxylates.Examples of anionic emulsifiers which may be mentioned are the productfrom Bayer AG which is commercially available under the name Baykanol®SL (=condensate of sulfonated ditolyl ether and formaldehyde) andphosphated or sulfated tristyrylphenol ethoxylates, with Soprophor SLK®and Soprophor® 4D 384 (Rhodia) being mentioned individually.

Other thinning agents which can be added to the thinning formulationsaccording to the invention and which may be mentioned are carbaryl,2-(1-naphthyl)acetic acid (NAA), benzyladenine, naphthyloxyacetic acid(NEA), gibberillic acid, paclobutrazole, ammonium thiosulfate and urea,and ethylene generators such as ethephon in apple varieties wherethinning is difficult or which tend to biennial bearing, such as Elstaror Red Delicious. Thinning formulations according to the invention whichcomprise ethephon in addition to metamitron must be emphasized for theuse of the thinning formulations according to the invention in thosecrops where thinning is difficult. In such a case, the thinningformulations advantageously comprise 100 to 1000 mg/l ethephon.

A growth regulator which can optionally be added and which may bementioned by way of example is prohexadione-calcium.

The addition, to the thinning formulations according to the invention,of foliar fertilizers, plant protection agents or plant strengtheningagents is especially advantageous. Those which may be mentioned are:calcium salts such as calcium chloride, calcium nitrate and theirformulations (for example Düngal®, Wuxal®, Basfoliar®, Bayfolan®),ammonium thiosulfate, ammonium nitrate, urea, iron chelates, magnesiumsulfate and trace minerals such as boron, zinc, manganese and the like,with urea being emphasized as particularly advantageous addition.

The use of calcium formate as foliar fertilizer in the fruit thinningformulations according to the invention should be particularlyemphasized. Calcium formate is especially inexpensive to purchase andavoids problems associated with the calcium salts conventionally used inagrochemical formulations. Thus, for example, calcium formate is nothygroscopic or contaminated by alkaline impurities (Ca(OH)₂), as is thecase with commercially available CaCl₂, where, indeed, intolerancesymptoms were observed when young plants were sprayed directly; it isalso less sparingly soluble in water than CaCO₃. Moreover, the newcalcium-formate-comprising formulations have better rainfastness thanthe conventionally used calcium salts (nitrate, carbonate and chloride).

Like the other calcium salts, the calcium formate which is applied,preferably sprayed, together with the thinning formulations according tothe invention onto young plant organs (leaves and fruits) is highlysuitable for avoiding calcium deficiency symptoms in the plants andabove all the fruits (for example bitter pit in apples) (see, forexample, Japanese Patent Specification No. J04-202080). Surprisingly,calcium formate is also particularly easy to formulate, and plantintolerance symptoms were not observed.

The thinning formulations according to the invention thereforepreferably comprise 0.1 to 50 g/l (0.01-5% by weight) of calciumformate, a calcium content of 1 to 20 g/l being especially preferred.

Agrochemical active substances which can additionally be added to thethinning formulations according to the invention are, for example,fungicides and insecticides, depending on the application in question.

Examples of fungicides which may be mentioned are sulfur (wettablesulfur), copper preparations, benzimidazole, bitertanol, dichlofluanid,fenarimol, fenhexamid, fludioxonil, fosetyl-aluminum, iprodione,myclobutanil, penconazole, triadimenol, vinclozolin, tolylfluanid(Euparen M®), captan, propineb, trifloxystrobin, kresoxim-methyl,dithianon, cyprodinil, pyrimethanil, mancozeb (Dithane Ultra®) andmetiram, with tolylfluanid being especially emphasized.

Examples of insecticides which may be mentioned are dimethoate,oxydemeton-methyl, malathion, parathion-methyl, phosphamidon,permethrin, amitraz, clofentezin, cyhalothrin, beta-cyfluthrin,fenproximate, diflubenzuron, tebufenozide, imidacloprid, thiacloprid,thiametoxam, clofentezine, fenoxycarb, parathion-methyl, XenTari®,tebufenozide, diflubenzuron, pirimicarb, tebufenpyrad, fenpyroximate,rapeseed oil, mineral oil and lecithin, with imidacloprid andthiacloprid being especially emphasized.

The thinning formulations according to the invention are prepared insuch a way that the components are mixed with each other in the ratiosdesired in each case.

In the preparation of the thinning formulations according to theinvention, the temperatures can be varied within a certain range. Ingeneral, they are prepared at temperatures between 10° C. and 50° C.,preferably at room temperature.

For the purpose of their application, the thinning formulationsaccording to the invention are advantageously prepared from WP, WG, SLand SC formulations of the active substances and additives by dissolvingthe formulation in a solvent, preferably water. Application is effectedby customary methods, for example by spraying, pouring, atomizing,injecting, painting of the emulsions, suspensions, solutions or aerosolsprepared.

The application rate of water for the thinning formulations according tothe invention can be varied within a substantial range. It depends ineach case on the active substances present and on their concentration inthe formulations. An application rate of 500 to 1500 1/ha is thought ofas preferred. As a rule, the application rate for the thinningformulations according to the invention is 1000 1/ha. However, lowerwater application rates of 100 to 300 1 may also be employed in certaincultivation methods.

This means that, ideally, 0.05 to 0.4 kg/ha (preferably 0.1 to 0.375kg/ha, especially preferably 0.2 to 0.35 kg/ha) of metamitron is appliedin the method according to the invention.

Conventional equipment employed for preparing agrochemical formulationsis suitable for the preparation of the thinning formulations accordingto the invention.

However, the formulations according to the invention can not only beused for thinning fruit in the method according to the invention, butcan, depending on the circumstances, be used as early as from theflowering period (floral thinning).

In the method according to the invention, application to the plantorgans is advantageously carried out by spraying the formulationsaccording to the invention. In this case, the plant organs, inparticular the leaves or fruits, are sprayed directly.

The uptake of calcium from the calcium-formate-comprising formulationsaccording to the invention is particularly efficacious at the earlyspraying dates conventionally used for thinning.

The method according to the invention is particularly suitable forthinning fruit in pome fruit crops. Crops and varieties which may beexplicitly mentioned are: all apple varieties (for example Boskoop,Braeburn, Cox Orange, Elstar, Gala, Gloster, Golden Delicious, Fuji,Jamba, James Grieve, Jonagold, Jonathan, Lobo, McIntosh, Red Delicious,Spartan), all pear varieties (for example Conference), quince andAsiatic pear. There is also a suitability for the stone fruit cropspeach and plum, and for olive, pistachios, kiwi fruit, grapevines orcitrus crops (for example tangerines).

The invention is illustrated by the examples which follow.

EXAMPLES

Thinning Formulations

A given amount of metamitron is mixed with the desired amounts ofadditives (for example urea, silicone surfactants) and made up to thedesired concentration with water. The standards are likewise prepared bydissolving the commercially available active substances in water.

Thus, for example, the following thinning formulations were prepared.

Formulation 1 (In Accordance with the Invention)

Aqueous spray mixture comprising 350 mg/l metamitron, 9 g/l urea, 60mg/l of a silicone surfactant.

Formulation 2 (In Accordance with the Invention)

Aqueous spray mixture comprising 350 mg/l metamitron, 2 g/l urea.

Formulation 3 (Not in Accordance with the Invention, Only ModeratelyTolerated by Plants)

Aqueous spray mixture comprising 700 mg/l metamitron, 2 g/l urea.

Formulation 4 (Not in Accordance with The Invention, Standard)

Aqueous spray mixture comprising 350 mg/l metamitron.

Formulation 5 (Not in Accordance with the Invention, Standard)

Aqueous spray mixture comprising 800 mg/l Amid-Thin® and 300 mg/lethephon.

Formulation 6 (Not In Accordance with the Invention, Standard)

Aqueous spray mixture comprising 850 mg/l carbaryl (Sevin®).

Biological Action

The following thinning results were obtained for the abovementionedformulations in spraying experiments on apples cv. Golden Delicious inthe production region “Altes Land” (Germany).

TABLE Result of the intermediate assessment after June drop for theeffect of metamitron formulations on the thinning of Golden Delicious(Altes Land). Water application rate: 1000 l/ha. Active compoundCropping No. Variant concentration (% of the control) 1 Control — 100 2Formulation 1 350 ppm 76 3 Formulation 2 350 ppm 82 4 Formulation 3 700ppm 85 5 Formulation 4 350 ppm 112 6 Formulation 5 800 + 106 300 ppm 7Formulation 1 350 ppm 42 8 Formulation 2 350 ppm 33 9 Formulation 3 700ppm 36 10 Formulation 4 350 ppm 41 11 Formulation 6 850 ppm 70 No. 2–6:Floral thinning No. 7–11: Fruit thinning

The data show that the formulations according to the inventiondemonstrate superior thinning in comparison with the standards. Thisadvantageous thinning effect is even more pronounced at the laterapplication during the 10-12 mm fruit stage.

Plant Tolerance

According to visual scoring, formulations comprising 350 mg/l metamitronshow no or only minimal damage when used in thinning experiments on awide range of apple varieties, while formulations comprising 700 mg/lmetamitron cause minimal to clearly discernable damage under identicalconditions.

We claim:
 1. A method for thinning fruits of apples or pears comprisingapplying at a later fruiting stage of 8 to 30 mm fruit size a thinningformulation comprising 50 to 400 mg/l metamitron to plant organs.
 2. Themethod of claim 1 wherein said thinning formulation is applied at a rateof 0.05 to 0.4 kg/ha metamitron to plant organs.
 3. The method of claim1 wherein the thinning formulation comprises 100 to 375 mg/l metamitron.4. The method of claim 3 wherein the thinning formulation comprises 150to 375 mg/l metamitron.
 5. The method of claim 1 wherein the thinningformulation further comprises 0.1 to 50 g/l calcium formate.
 6. Themethod of claim 5 wherein the thinning formulation comprises 1 to 20 g/lcalcium formate.
 7. The method of claim 1 wherein the later fruitingstage is an 8 to 17 mm fruit size.
 8. The method of claim 7 wherein thelater fruiting stage is a 10 to 12 mm fruit size.
 9. The method of claim1, wherein no or only minimal foliar necroses are observed in the methodfor thinning fruits.
 10. The method of claim 1, wherein no foliarnecroses are observed in the method for thinning fruits.
 11. A fruitthinning formulation, comprising 50 to 400 mg/l metamitron and 0.1 to 50g/l calcium formate.
 12. The fruit thinning formulation as claimed inclaim 11, comprising 1 to 20 g/l calcium formate.